Limit switch



Dec. 13, 1966 B. R. WANLASS LIMIT SWITCH 2 Sheets-Sheet 1 Filed June 15, 1964 INVENTOR.

582? R; lL/onZass BY 6 g? a W HA5 ATTORNEY Dec. 13, 1966 B. R. WANLASS 3,291,929

LIMIT SWITCH Filed June 15, 1964 2 Sheets-Sheet 23 INVENTOR. 5

562? A. Man/0.51s BY H16 ATTORNEY United States Patent 3,291,929 LIMIT SWITCH Bert R. Wanlass, Warren, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed June 15, 1964, Ser. No. 374,911 2 Claims. (Cl. 200-67) This invention relates to electrical limit switches and more particularly to a type of electrical switch adapted to switch circuits carrying high amperage loads.

It is desirable in design of limit switches that are used in conjunction with circuits carrying high amperage to carry out the switching action in a precise manner with the actual switching taking place very quickly to minimize arcing. It is also desirable in the design of switches to have a sliding action take place between the switching contacts in order to reduce the oxidation build-up on the contacts. The speed of the switching action is important to reduce the sparking that takes place as high amperage circuits come into close proximity with one another.

It is an object of the present invention to provide an improved limit switch that is push button actuated and in which the switching action takes place after a certain amount of movement has taken place by the actuator.

It is another object of the present invention to provide an improved limit switch in which the switching action takes place very rapidly and a wiping action is generated between the switch contacts during switch actuation.

It is still another object of the present invention to provide an improved push button actuated limit switch whose actuator is normally biased in one direction toward one contact and rapidly moves into engagement with another contact after the actuator has traveled a predetermined amount.

It is yet another object of the present invention to pro vide an improved limit switch that will carry out the aforementioned objects and has a minimum number of moving parts and, hence, is economical to manufacture.

It is a further object of the present invention to provide an improved limit switch that is substantially impervious to the deleterious effects of humidity and moisture.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a plan view of the subject invention;

FIGURE 2 is a side elevation of the subject invention;

FIGURE 3 is a sectional view taken along line 3-3 of FIGURE 1;

FIGURE 4 is a sectional view taken along line 33 of FIGURE 1 with the actuator shown in a depressed position;

FIGURE 5 is a sectional view taken along line 55 of FIGURE 2;

FIGURE 6 is a sectional view, with parts broken away, taken along line 6-6 of FIGURE 3;

FIGURE 7 is a sectional view taken along line 77 of FIGURE 5 FIGURE 8 is a side elevation of the subject invention;

FIGURE 9 is a side elevation of the subject invention viewed from the opposite side of the switch seen in FIGURE 8.

Referring now to FIGURE 1, a switch body 10 is shown as mounted on a panel 12 is any well-known manner. An actuator 14 is seen in its operative position relative to the panel 12.

Referring now to FIGURE 2, a series of terminals 16 are illustrated in conductive relationship with a plurality of contacts 18 that attach the terminals 16 to a wall of the switch body 10. One of the terminals 16, for example, connected to a power source, not shown, is attached to a wall of the switch body 10 by means of a. contact rivet 19.

7 Referring now to FIGURE 3, the actuator 14 is illustrated as carrying a serrated pin 20 disposed in a pocket 22 formed in one end of the actuator 14. The serrated pin 20 frictionally engages the walls of the pocket 22 and is adapted to be permanently pressed into frictional engagement with a portion of the pocket 22 when the switch is initially mounted in its operative environment. A moving member, not shown, will make contact with the pin 20 and will serve to move the actuator 14 into the switch body. A spring 24 is biased against a portion of the switch body and the underside of the actuator 14 to provide a return means for the actuator as it is moved into the switch body by pressure being exerted on the serrated pin 20.

A conductive member 26 is pivotally mounted on a wall of the switch body 10 and is arranged to pivot around the contact rivet 19. The pivotable member 26 carries a contact 28 which is hereinafter referred to as a movable contact. The contact rivets 18, previously described, have an end disposed in opposition to the movable contact 28 and will hereinafter be referred to as the fixed contacts.

A resilient means or spring 30 is pivotally carried on a pivot post 32 formed on a surface of the actuator 14. An opposite end of the spring 30 cooperates with an aperture 34 formed on an opposite end of the conductive member 26 from the end in which the movable contact 28 is disposed.

An upstanding flange 36, formed as an extension of the terminal 16 engaging the contact rivet, extends into the switch body and cooperates with a slot 38 of arcuate shape formed in the conductive member 26. The relationship of the conductive member 26 and the contact rivet 19 and terminal 16 is more clearly illustrated in FIGURE 6.

Referring now to FIGURE 7, the actuator 14 is seen to have a T-shaped portion 40 arranged to slide in a keyway 42 formed in one Wall of the switch body 10. In this manner, the actuator is laterally located for sliding movement of a translational nature as pressure is put on the serrated pin 20.

Referring now to FIGURE 5, the actuator 14 is seen to have an overall dimension in cross section substantially equal to the dimension of an aperture 44 formed in one end of the switch body 10.

In operation, the subject invention is mounted on a panel or member 12 in an operative location Where it can be struck by a moving member whose travel is to be limited. This could be, for example, a moving portion of a convertible top on an automobile. As the moving member, whose travel is to be limited, strikes the serrated pin 20 during the initial installation of the switch, the frictional resistance between the serrations and the pocket 24 is greater than the force needed to compress the spring 24. Therefore, the actuator 14 will be driven into the switch body until the actuator bottoms out on a Wall 25 of the switch body. If further travel of the moving member, whose travel is to be limited, is necessary, this extra movement will move the serrated pin 20 to some point within the pocket 22 and, thereafter, in that particular installation, will maintain that adjusted position. This adjustment of the pin 20 relative to the actuator 14 could be accomplished by manual movement of the member whose travel is to be limited or might be accomplished by measuring devices which would establish the exact relationship of parts. In this manner, the switch is enabled to be mounted in an operative environment where slight dimensional inaccuracies in the mounting structure are automatically compensated for.

Referring now to FIGURE 3, the subject invention is illustrated in a position it will assume when no pressure is exerted on the pin 20 and the movable contact 28 is conductively engaging one of the fixed contacts 18. Power is supplied through the contact rivet 19 into the conductive member 26 and it becomes therefore apparent that a path for current flow is established between the power source in conductive relationship with the rivet 19 and a power operable means in conductive relationship with one of the contacts 18.

When pressure is exerted on the pin 20 by a member whose travel is to be limited, the actuator 14 is driven downwardly until it assumes a position as viewed in FIG- URE 4. On its way to this position, as the pivot post 32 moves past a line. passing through the aperture 34 and the contact rivet 19, the spring 30 will very quickly pivot the conductive member 26 in a snap-acting manner into a position as viewed in FIGURE 4. A preset alignment is established between the bottomed actuator 14, the movable contact 28 and one of the fixed contacts 18, and the relationship of the flange 36 and the slot 38. This is accomplished in order to positively locate the conductive member 26 and the movable contact 28 with the fixed contacts 18. It should be noted that the aforementioned line, established between the aperture 34 and the pivot point 19, will not be crossed by the pivot post 32 until the actuator 14 has practically completed its movement. This is important in that it allows a moving member, whose movement is to be limited, to be very positively and precisely stopped at a predetermined point.

When the moving member is moved away from the switch body 10, the serrated pin '20 will follow that movement through a force provided by the return spring 24. When this return motion is practically completed and the pivot post 32 moves past the newly established line defined by the aperture '34 and the rivet 19, a snap action will again take place and the conductive member 26 will assume a position as illustrated in FIGURE 3.

The subject invention finds utility in an environment where the movement of some member is sought to be controlled. Such an environment might be the linkage mechanism controlling the positioning of a convertible top on an automobile. In this environment, a moving member would be in contact with the serrated pin 20 and would be moved to either extreme of movement by an auxiliary motor. This auxiliary motor could, for example, be an electric motor having a reversible drive. The switch could be positioned in a circuit to this motor with the terminal 16 held by the rivet 19 connected to a source of power and the contacts 18 through the terminal 16 connected thereto being disposed in a circuit controlling the direction of rotation of the motor. It is thus seen that, as an object moved by the motor approached a predetermined point during which time the pin 20 was being driven into the switch body, a snap-action switching' action could be generated which would very quickly cut oif power to either direction of drive of the motor. The foregoing is ofiered to illustrate a specific operative environment for the subject invention and is not meant to limit the operation or utility of the switch to that environment.

It is also an important feature of the subject device that the switch body can be -substantially enclosed and any parts, exposed to an area outside the switch body, could be easily sealed. This sealing would serve the dual purpose of preventing foreign material from entering the switch body and would also serve to keep the switching area of the subject invention substantially free of moisture. This is a desirable feature in view of the propensity of high amperage circuits, as herein described, to are as contacts switching such circuits approach contact with one another.

It is also to be noted, as a particularly advantageous feature of the subject device, that the switching action is generated with a sliding motion of a movable contact across one or more fixed contacts. This is generally referred to as a wiping action and serves to destroy the oxidation build-up on electrical contacts before the conductive path established between such contacts can be adversely affected. It becomes therefore apparent that the subject invention combines switching features in one switch that are normally found only in separate switches. These features are, more specifically, a snap-action switching of contacts for high amperage installations and a contact-wiping action normally associated with low amperage circuits. 1

While the embodiment of the present invention, as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An electric switch comprising: a switch body; actuator means slidably disposed for translational movement in said switch body; fixed contacts spaced apart and carried by the switch body, said fixed contacts being adapted to be connected respectively to an electrical load, conductive means pivotally mounted on a portion of the switch body at a point equidistant from said'fixed contacts, said conductive means carrying a contact movable in an arcuate path between the fixed contacts; locating means including a slot formed in said conductive means for positioning said conductive means positively with respect to any one of the fixed contacts; and resilient means including means comprising a substantially U-shaped portion having one end pivotally engaging said actuator means and having another end pivotally engaging said conductive means, said resilient means being responsive to sliding movement of the actuator means near either extreme of translational movement to rapidly drive the movable contact into sliding engagement with any of the spaced fixed contacts.

2. An electric switch comprising: a switch body having an opening in one end thereof; actuator means slidably disposed for translational movement between two extremes on said switch body, said actuator means having a portion extending through the opening in the switch body and including an end adapted to be pressed by an actuating impulse from outside the switch body; at least two fixed contacts spatially disposed on an inside surface of the switch body and adapted to be electrically connected to external electrical circuits; conductive means pivotally mounted on a portion of the switch body and including a contact on one end thereof adapted to be moved in an arcuate path between the fixed contacts in response to movement of the actuator means, said conductive means having a slot arranged to cooperate with a stationary portion of the switch body during pivotal movement of the conductive means to positively locate the movable contact in engagement with any selected fixed contact; and a resilient overcentering U-shaped spring pivotally engaging the actuator means and the conductive means at points on opposite sides of the pivotal mounting of said conductive means to snap the movable contact into sliding engagement with the fixed contacts as the conductive means pivots in response to translational movement of the actuator means as it 3,049,600 8/1962 Fraser. approaches either extreme of movement. FOREIGN PATENTS References Cited by the Examiner 96,076 4/ 1 wi Z rl n UNITED STATES PATENTS 5 ROBERT K. SCI-IAEFER, Primary Examiner. 501,450 7/1893 Stanley. 1,119,043 12/1914 Russell 200-73 KATHLEEN CLAFFY Exammer- 2,151,612 3/1939 Morris 200-159 D. SMITH, JR., Assistant Examiner.

2,441,924 5/1948 Steinback. 

1. AN ELECTRIC SWITCH COMPRISING: A SWITCH BODY; ACTUATOR MEANS SLIDABLY DISPOSED FOR TRANSLATIONAL MOVEMENT IN SAID SWITCH BODY; FIXED CONTACTS SPACED APART AND CARRIED BY THE SWITCH BODY, SAID FIXED CONTACTS BEING ADAPTED TO BE CONNECTED RESPECTIVELY TO AN ELECTRICAL LOAD, CONDUCTIVE MEANS PIVOTALLY MOUNTED ON A PORTION OF THE SWITCH BODY AT A POINT EQUIDISTANT FROM SAID FIXED CONTACTS, SAID CONDUCTIVE MEANS CARRYING A CONTACT MOVABLE IN AN ARCUATE PATH BETWEEN THE FIXED CONTACTS; LOCATING MEANS INCLUDING A SLOT FORMED IN SAID CONDUCTIVE MEANS FOR POSITIONING SAID CONDUCTIVE MEANS POSITIVELY WITH RESPECT TO ANY ONE OF THE FIXED CONTACTS; AND RESILIENT MEANS INCLUDING MEANS COMPRISING A SUBSTANTIALLY U-SHAPED PORTION HAVING ONE END PIVOTALLY ENGAGING SAID ACTUATOR MEANS AND HAVING ANOTHER END PIVOTALLY ENGAGING SAID CONDUCTIVE MEANS, SAID RESILIENT MEANS BEING RESPONSIVE TO SLIDING MOVEMENT OF THE ACTUATOR MEANS NEAR EITHER EXTREME OF TRANSLATIONAL MOVEMENT TO RAPIDLY DRIVE THE MOVABLE CONTACT INTO SLIDING ENGAGEMENT WITH ANY OF THE SPACED FIXED CONTACTS. 